Secondary battery pack with improved thermal management

ABSTRACT

The present invention relates to a novel secondary battery pack with improved thermal management useful for an all-electric vehicle (EV), a plug-in hybrid vehicle (PHEV), a hybrid vehicle (HEV), or battery packs used for other vehicles batteries, and more particularly, to the use of a specific material for thermally insulating a secondary battery pack and further minimizing the propagation of thermal runaway within a battery pack.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/534,730, filed Nov. 24, 2021, which is a continuation of U.S. patentapplication Ser. No. 16/673,628, filed Nov. 4, 2019, now U.S. Pat. No.11,261,309, issued Mar. 1, 2022, which is a continuation of U.S. patentapplication Ser. No. 15/891,037, filed Feb. 7, 2018, now U.S. Pat. No.10,501,597, issued Dec. 10, 2019, which claims priority to U.S.Provisional Ser. No. 62/456,502 filed Feb. 8, 2017. The contents of eachof which are incorporated herein by reference in their entirety for allpurposes.

FIELD OF THE INVENTION

The present invention relates to a novel secondary battery pack, inparticular those comprising lithium-ion battery cells, with improvedthermal management allowing the use under extended conditions oftemperature extremes. More particularly, the invention relates to theuse of a specific material for thermally insulating a secondary batterypack and further minimizing the propagation of thermal excursions withina battery pack. Said secondary battery pack could be used in anall-electric vehicle (EV), a plug-in hybrid vehicle (PHEV), a hybridvehicle (HEV), or for other vehicles batteries.

BACKGROUND OF THE INVENTION

Batteries can be broadly classified into primary and secondarybatteries. Primary batteries, also referred to as disposable batteries,are intended to be used until depleted, after which they are simplyreplaced with one or more new batteries. Secondary batteries, morecommonly referred to as rechargeable batteries, are capable of beingrepeatedly recharged and reused, therefore offering economic,environmental and ease-of-use benefits compared to a disposable battery.Examples of the secondary batteries may include nickel-cadmiumbatteries, nickel-metal hybrid batteries, nickel-hydrogen batteries,lithium secondary batteries, etc.

Secondary batteries, in particular lithium-ion batteries, have emergedas a key energy storage technology and are now the main technology forconsumer electronics devices, industrial, transportation, andpower-storage applications.

Due to their high potential and their high energy and power densities,and also their good lifetime, secondary batteries are now the preferredbattery technology, in particular in the automotive industry as it isnow possible to provide longer driving range and suitable accelerationfor electrically propelled vehicles such as Hybrid Electric Vehicles(HEVs), Battery Electric Vehicles (BEVs) and Plug-In Hybrid ElectricVehicles (PHEVs). In current automotive industry, different sizes andshapes of lithium-ion battery cells are being manufactured and aresubsequently assembled into packs of different configurations. Anautomotive secondary battery pack typically consists of a large numberof battery cells, sometimes several hundreds, even thousands, to meetdesired power and capacity needs.

This switch in drive train technology is not, however, without itstechnological hurdles as the use of an electric motor translates to theneed for inexpensive batteries with high energy densities, longoperating lifetimes, and capability of operating in a wide range ofconditions. Although rechargeable battery cells offer a number ofadvantages over disposable batteries, this type of battery is notwithout its drawbacks. In general, most of the disadvantages associatedwith rechargeable batteries are due to the battery chemistries employed,as these chemistries tend to be less stable than those used in primarycells. Secondary battery cells such as lithium-ion cells tend to be moreprone to thermal management issues which occur when elevatedtemperatures trigger heat-generating exothermic reactions, raising thetemperature further and potentially triggering more deleteriousreactions. During such an event, a large amount of thermal energy israpidly released, heating the entire cell up to a temperature of 850° C.or more. Due to the increased temperature of the cell undergoing thistemperature increase, the temperature of adjacent cells within thebattery pack will also increase. If the temperature of these adjacentcells is allowed to increase unimpeded, they may also enter into anunacceptable state with exceedingly high temperatures within the cell,leading to a cascading effect where the initiation of temperatureincreases within a single cell propagate throughout the entire batterypack. As a result, power from the battery pack is interrupted and thesystem employing the battery pack is more likely to incur extensivecollateral damage due to the scale of damage and the associated releaseof thermal energy. In a worst case scenario, the amount of generatedheat is great enough to lead to the combustion of the battery as well asmaterials in proximity to the battery.

Furthermore, due to the characteristics of the lithium ion batteries,the secondary battery pack operates within an ambient temperature rangeof −20° C. to 60° C. However, even when operating within thistemperature range, the secondary battery pack may begin to lose itscapacity or ability to charge or discharge should the ambienttemperature fall below 0° C. Depending on the ambient temperature, thelife cycle capacity or charge/discharge capability of the battery may begreatly reduced as the temperature stays below 0° C. Nonetheless, it maybe unavoidable that the lithium ion battery be used where the ambienttemperature falls outside the optimum ambient temperature range which isbetween 20° C. to 25° C. These factors not only greatly shorten thedriving range of vehicle, but also cause a great damage to batteryDeterioration in energy and power available at lower temperatures isattributed to reduction in capacity and increase in internal resistance.

Alluding to the above, in a battery or battery assembly with multiplecells, significant temperature variances can occur from one cell to thenext, which is detrimental to performance of the battery pack. Topromote long life of the entire battery pack, the cells must be below adesired threshold temperature. To promote pack performance, thedifferential temperature between the cells in the secondary battery packshould be minimized. However, depending on the thermal path to ambient,different cells will reach different temperatures. Further, for the samereasons, different cells reach different temperatures during thecharging process. Accordingly, if one cell is at an increasedtemperature with respect to the other cells, its charge or dischargeefficiency will be different, and, therefore, it may charge or dischargefaster than the other cells. This will lead to decline in theperformance of the entire pack.

A number of approaches have been employed to either reduce the risk ofthermal issues, or reduce the risk of thermal propagation. These can befound in U.S. Pat. No. 8,367,233 which discloses a battery pack thermalmanagement system that comprises at least one enclosure failure portintegrated into at least one wall of a battery pack enclosure, where theenclosure failure port(s) remains closed during normal operation of thebattery pack, and opens during a battery pack thermal event, therebyproviding a flow path for hot gas generated during the thermal event tobe exhausted out of the battery pack enclosure in a controlled fashion.

Another approach is to develop new cell chemistries and/or modifyexisting cell chemistries. Yet another approach is to provide additionalshielding at the cell level, thus inhibiting the flow of thermal energyfrom the cell undergoing thermal management issues propagating toadjacent cells. Still yet another approach, is to use a spacer assemblyto maintain the position of the battery undergoing the thermal event inits predetermined location within the battery pack, thereby helping tominimize the thermal effects on adjacent cells.

Thermally insulating a battery pack has also been described to reducethe risk of thermal excursions or their propagation. For example,document US 2007/0259258 describes a battery of lithium generators inwhich the generators are stacked one on another and this stack is heldin position being surrounded by polyurethane foam. An embodiment is alsodisclosed in which cooling fins are inserted between two generators.

Document DE 202005010708 describes a starter lead-acid electrochemicalgenerator and an electrochemical generator for industrial use whosehousing contains plastic foam such as polypropylene or polyvinylchloride having closed pores.

Document US2012/0003508 describes a battery of lithium electrochemicalgenerators including a casing; a plurality of lithium electrochemicalgenerators housed in the casing, each generator including a container; arigid, flame-retardant foam with closed porosity formed of anelectrically insulating material filling the space between the innerwall of the casing and the free surface of the side wall of thecontainer of each electrochemical generator, the foam covering the freesurface of the side wall of the container of each electrochemicalgenerator over a length representing at least 25% of the height of thecontainer. According to one embodiment, the foam consists of a materialchosen from the group comprising polyurethane, epoxy, polyethylene,melamine, polyester, formophenol, polystyrene, silicone or a mixturethereof, polyurethane and the mixture of polyurethane and epoxy beingpreferred. The expansion of polyurethane resin for foam-form isdescribed using the following chemical routes to obtain the foam:

-   -   a) via chemical route, i.e. the reaction of water on isocyanate        producing CO₂ which will cause the polyurethane to foam;    -   b) via physical route, i.e. vaporization of a liquid with low        boiling point under the action of heat produced by the        exothermal reaction between isocyanate and the hydrogen-donor        compound, or    -   c) via injection of air.

However, rigid foams which are typically produced by reacting forexample a polyisocyanate with an isocyanate reactive material such aspolyol in the presence of a blowing agent do not exhibit the highcompression set required when foams are used to minimize the adverseeffect of any fire and explosion linked to a thermal event.

In document U.S. Pat. No. 4,418,127 a modular lithium battery isdescribed and having a plurality of cells, having electrical connectingmeans connecting the cells to output terminals, and venting means forreleasing discharge byproducts to a chemical scrubber. Stainless steelcell casings are potted in an aluminum modular case with a syntacticepoxy foam, said foam being syntactic in nature to reduce weight andwhich has incorporated therein microballoons composed of compositionsselected from the group consisting of glass and ceramics, and additivesto reduce flammability.

Another major issue in the emerging electrical vehicle field is linkedto the drivetrains used which integrate motor, automated manualtransmission, shafts, and wheels with the final drive to control speedand generate larger torque for driving the vehicle. The main differencecompared to traditional fuel-consuming vehicles is that there is noclutch or hydraulic torque converter in electric vehicles so the overallsystem configuration is less elastic inherently as the motor and thetransmission system are directly mechanically coupled. Thisconfiguration has little passive damping effect that can dampendisturbances and avoid oscillations, which are mostly noticeable duringtravel in the low speed range. Indeed, the dominating sound is themagnetic noise which generates a whining noise at high frequencies. Avehicle running only with an electric motor will also have less maskingsound at low frequencies. This means that other noise requirements onfor example component noise such as liquid or air cooling/heating forthe electrical batteries must be changed accordingly. The noise duringregeneration (battery charging) at coast down is also important.Therefore, due to the low damping in an electrical vehicle and lack ofpassive damping hardware as compared with a conventional vehicle, adamping control strategy is needed to minimize the drivetrainoscillations.

While a number of approaches have been adopted to try to lower the riskof thermal incursions as well as thermal energy propagation throughoutthe battery pack, it is critical that if a pack-level thermal event doesoccur, personal and property risks are minimized. As the number of cellsin a battery increases, and as the size of the cells increases, so doesthe necessity and benefit of providing suitable thermal management.

Furthermore, there is still a need to better insulate battery cells, inparticular lithium-ion batteries from the adverse effect of lowtemperature that are met when the weather reaches severe low temperaturethat could reach −20° C. and even lower.

In this context, one of the essential objectives of the presentinvention is to provide a new battery pack that will provide suitablethermal management and minimize personal and property risks due touncontrolled thermal events as it is still awaited.

Another essential objective of the invention is to provide a new batterypack that will provide damping control to minimize the drivetrainoscillations and a better efficiency in controlling the propagation ofnoise arising from electrical batteries while they are used.

With the present invention, it is sought that the claimed secondarybattery pack will address said problems linked to uncontrolled thermalexcursions, in particular for lithium batteries, will present efficientlow temperature insulation properties and will provide a damping controlstrategy to minimize the drivetrain oscillations.

All these objectives, among others, are achieved by the presentinvention, which relates to a secondary battery pack comprising:

-   -   at least one battery module casing 102 in which is disposed a        plurality of battery cells 103 which are electrically connected        to one another,    -   a silicone rubber syntactic foam comprising a silicone rubber        binder and hollow glass beads, and said silicone rubber        syntactic foam fills partially or fully the open space of said        battery module casing 102 and/or covering partially or totally        said battery cells 103 and/or covering partially or totally said        module casing 102, and    -   optionally a lid covering the battery module casing 102.

To achieve this objective, the Applicant demonstrated, to its credit,entirely surprisingly and unexpectedly, that the choice of siliconerubber as a binder for a syntactic foam comprising hollow glass beadsmakes it possible to overcome problems that were not solved by similarbatteries using organic rubber syntactic foam.

As used herein, the term “silicone rubber” includes the crosslinkedproduct of any crosslinkable silicone composition. By “silicone rubbersyntactic foam” it is meant a matrix made of silicone rubber in which isdispersed hollow glass beads.

Furthermore, it is well known that the driving range of an electricvehicle between charges is calculated at ambient temperature. Electricvehicle drivers are being made aware that frigid temperature reduces theavailable mileage. This loss is not only caused by heating the cabinelectrically but by the inherent slowing of the battery'selectrochemical reaction, which reduces the capacity while cold. So, thespecific choice of silicone rubber as a binder within said syntacticfoam makes it possible for said foam to exhibits excellent insulation inregards to low temperature close or below the freezing point.

Another advantage of using silicone rubber binders over organic rubberbinders for a syntactic foam could be exemplified with the embrittlement(or loss of ductility) point, which is between −20° C. to −30° C. fortypical organic rubber binder compared to −60° C. to −70° C. for bindersaccording to the invention.

Another advantage is also linked to physical properties such aselasticity which remain efficient for a silicone rubber binder even attemperatures at which organic rubber binders turn brittle.

Another advantage of using a silicone syntactic foam according to theinvention is that it has a very low water absorption and hence doesisolate perfectly the battery cells from undesired water for its optimumuses. Indeed, contrary to silicone syntactic foams, a standard siliconefoam contains only blown gas bubbles and have the voids completely, orat least partly, connected to each other, so with an ability to absorband diffuse water, feature that makes it difficult to use it within anelectrical vehicle in which the battery packs are most often positionedunderneath the vehicle or in the vehicle floor and then rainy drivingconditions could raise issues with such materials.

As differences in temperatures affect the resistance, self-dischargerate, coulombic efficiency, as well as the irreversible capacity andpower fade rates of battery cells, over a wide range of chemistries, thesecondary battery pack according to the invention allows for uniformthermal conditions for all cells in a battery pack or module. Thelikelihood of cell state of charge imbalance and of early failure ofnon-defective cells is therefore further minimized.

According to a preferred embodiment, said silicone rubber syntactic foamis used as a potting material disposed either in said battery modulecasing 102 to at least partially encapsulate said plurality of batterycells 103 and/or outside the battery module casing 102 so as to at leastpartially encapsulate the said battery module casing 102.

Indeed, the silicone rubber syntactic foam fills partially or fully theopen space of said battery module casing and/or covering partially ortotally said battery cells. The silicone rubber binder provides thesyntactic foam with mechanical flexibility and thermal stability over abroad temperature range (e.g. from −70° C. to 200° C.). Additionally,the decomposition of the silicone rubber binder at temperatures ofthermal excess (up to 850° C.) into silicon dioxide and silicon oxideabsorbs a large amount of heat. Therefore, the heat diffusion from theunit cell to the neighboring unit cells can be effectively insulated bya thermal insulation barrier which is said silicone rubber syntacticfoam. The thermal excursions are not propagated through the entirebattery module and then threatening the safety of the user is thusprevented. In addition, for some battery modules having control circuitboards disposed in the battery module casing, the silicone rubbersyntactic foam of the disclosure can be disposed between the batterycells and the circuit board and between battery cells and the connectingcircuit to reduce the battery heating problem caused by the circuitboard and the circuit.

The silicone formulation contains hollow glass beads and in a preferredembodiment said hollow glass beads have melting points similar to thatof a thermal event occurring in a battery or a group of batteries in apack so heating will soften and melt the glass reducing heat transferand protecting other batteries around the overheating battery.

According to a preferred embodiment, said battery cells 103 are oflithium-ion type.

According to another preferred embodiment, the secondary battery packaccording to invention, further comprising a plurality of heatdissipation members which are disposed at two or more interfaces betweenthe battery cells, and at least one heat exchange member integrallyinterconnecting the heat dissipation members which is mounted to oneside of the battery module casing 102, whereby heat generated from thebattery cells during the charge and discharge of the battery cells isremoved by the heat exchange member. It allows for cooling of thebattery cells with higher efficiency than conventional cooling systemseven with no spaces between the battery cells or with very small spacesbetween the battery cells, thereby maximizing heat dissipationefficiency of the secondary battery pack and allowing to further limitfree space within said secondary battery pack.

According to another preferred embodiment, the heat dissipation membersaccording to the invention are made of a thermally conductive materialexhibiting high thermal conductivity and the heat exchange member isprovided with one or more coolant channels for allowing a coolant suchas a liquid or a gas to flow there.

Heat dissipation members according to the invention are not particularlyrestricted as long as each of the heat dissipation members is made of athermally conductive material such as a metal plate exhibiting highthermal conductivity.

Preferably, the heat exchange member is provided with one or morecoolant channels for allowing a coolant to flow there through. Forexample, coolant channels for allowing a liquid coolant, such as water,to flow there through may be formed in the heat exchange member, therebyproviding an excellent cooling effect with high reliability as comparedwith a conventional air-cooling structure.

According to another preferred embodiment, the secondary battery packaccording to the invention, further comprising a coolant inlet manifold,a coolant outlet manifold and a plurality of thermal exchange tubes asheat dissipation members and extending between the inlet and outletmanifolds, said thermal exchange tubes are disposed at one or moreinterfaces between the battery cells and have a coolant passing throughto exchange heat generated from the battery cells during the charge anddischarge of the battery cells.

Hollow glass beads are employed in the syntactic foam of this invention,and function to reduce the density of the foam. Hollow glass beads, andin particular hollow glass microspheres are well suited for thisapplication because, in addition to having excellent isotropiccompressive strengths, they have the lowest density of any filler thatwould be useful in the manufacture of high compressive strengthsyntactic foam. The combination of high compressive strength and lowdensity make hollow glass microspheres the filler with numerousadvantages according to the invention.

According to one embodiment, hollow glass beads are hollow borosilicateglass microspheres also known as glass bubbles or glass microbubbles.

According to another embodiment, the hollow borosilicate glassmicrospheres have true densities ranging from 0.10 gram per cubiccentimeter (g/cc) to 0.65 gram per cubic centimeter (g/cc).

The terms “true density” is the quotient obtained by dividing the massof a sample of glass bubbles by the true volume of that mass of glassbubbles as measured by a gas pycnometer. The “true volume” is theaggregate total volume of the glass bubbles, not the bulk volume.

According to another embodiment, the level of hollow glass beads is upto 80% volume loading in the silicone rubber syntactic foam or of theliquid crosslinkable silicone composition precursor of said siliconerubber syntactic foam as described below, and most preferably between 5%and 70% by volume of the silicone rubber syntactic foam or of the liquidcrosslinkable silicone composition precursor of said silicone rubbersyntactic foam as described below.

According to a preferred embodiment, hollow glass beads are chosen fromthe 3M™ Glass Bubbles Floated Series (A16/500, G18, A20/1000, H20/1000,D32/4500 and H50/10,000EPX glass bubbles products) and 3M™ Glass BubblesSeries (such as K1, K15, S15, S22, K20, K25, S32, S35, K37, XLD3000,S38, S38HS, S38XHS, K46, K42HS, S60, S60HS, iM16K and iM30K glassbubbles products) sold by 3M Company. Said glass bubbles exhibit variouscrush strengths ranging from 1.72 megapascal (250 psi) to 68.95megapascals (10,000 psi) at which ten percent by volume of the firstplurality of glass bubbles collapses.

According to a preferred embodiment said glass bubbles are chosen amongthose exhibiting crush strengths ranging from 1.72 megapascal (250 psi)to 68.95 megapascals (4000 psi) at which ten percent by volume of thefirst plurality of glass bubbles collapses.

According to a most preferred embodiment, hollow glass beads are chosenfrom the 3M™ Glass Bubbles series, S15, K25, S32 and XLD3000.

To fill the free spaces with silicone rubber syntactic foam according tothe invention, it is possible:

-   -   a) either to use a liquid crosslinkable silicone composition        precursor of a silicone rubber syntactic foam comprising hollow        glass beads according to the invention, which, after injection        or free flow comes to fill the free spaces and cures via        crosslinking,    -   b) or to use a machined or previously molded block of a silicone        rubber syntactic foam comprising hollow glass beads that is        inserted in the casing at the time of assembly.

The use of a liquid crosslinkable silicone composition precursor of asilicone rubber syntactic foam comprising hollow glass beads in thebattery facilitates the filling thereof compared with a standard liquidcrosslinkable silicone precursor of a silicone foam as the foamingprocess of a standard foam creates blown gas bubbles and have the voidscompletely, or at least partly, connected to each other which causesnumerous defects within the obtained silicone foam and filling problems.

Indeed, standard silicone foams are obtained by several methods, forexample, by adding a thermally decomposable blowing agent, or by moldingand curing while generating hydrogen gas by-product. In the method ofadding a thermally decomposable blowing agent, the toxicity and odor ofdecomposed gases are problems. The method of utilizing hydrogen gasby-product during the curing step suffers from such problems as thepotential explosion of hydrogen gas and the careful handling of uncuredcomposition during shelf storage. Further, the gas generating methodencounters difficulty in forming controlled uniform cells.

The use of expandable silicone rubber syntactic foam facilitates thefilling of empty space within the battery pack since the swell pressurepushes the foam into all the cavities and recesses of the geometry to befilled. Also, this method allows any geometry to be filled which is notpossible using prefabricated blocks.

Silicone rubber which is used as a binder within the syntactic foamaccording to the invention, are often referred to as siliconeelastomers, are composed of three to four essential ingredients. Theseingredients are (i) one or more reactive silicone polymer, (ii)eventually one or more filler(s) (iii) a crosslinking agent, and (iv) acatalyst. Generally, there exist two main types of silicone rubbercompositions which are heat vulcanized, (HTV) silicone rubber and roomtemperature vulcanizing (RTV) silicone rubber. Heat vulcanized or hightemperature vulcanizing (HTV) silicone rubber compositions are oftenfurther differentiated as high consistency rubber (HCR) or liquidsilicone rubber (LSR) depending on uncured viscosity of the composition.The terms “room temperature vulcanizing” (RTV) silicone rubbercompositions, however may be misleading as some RTV compositions canrequire a modicum of heat to progress the reaction at a reasonable rate.

The silicone rubber binder in which hollow glass beads are dispersed maybe obtained by curing either an addition curing type organopolysiloxanecomposition, a peroxide curing type organopolysiloxane composition or acondensation type organopolysiloxane composition.

Such silicone compositions are well known by those skilled in the art ofthe silicone field. The addition curing type organopolysiloxanecomposition is preferably defined as primarily comprising (1) 100 partsby weight of an organopolysiloxane having at least two alkenyl groupsattached to silicon atoms in a molecule, (2) 0.1 to 50 parts by weightof an organo-hydrogenpolysiloxane having at least two, preferably atleast three hydrogen atoms attached to silicon atoms (i.e., SiH groups)in a molecule, and (3) a catalytic amount of an addition reactioncatalyst. The peroxide curing type organopolysiloxane composition ispreferably defined as primarily comprising (1) 100 parts by weight of anorganopolysiloxane having at least two alkenyl groups attached tosilicon atoms in a molecule, and (2) a catalytic amount of an organicperoxide. The condensation type organopolysiloxane compositions thatcrosslink via polycondensation generally involve a silicone oil,generally a polydimethylsiloxane, with hydroxyl end groups, optionallyprefunctionalized with a silane so as to have hydrolyzable andcondensable ends and a crosslinking agent, a polycondensation catalyst,conventionally a tin salt or an alkyl titanate.

According to a preferred embodiment, said silicone rubber syntactic foamis obtained by curing an addition curing type organopolysiloxanecomposition X. This embodiment offers several advantages over one partsystems (condensation type organopolysiloxane compositions), especiallyin production environments. Since it is the catalyst and not moisture,as in the case of a condensation curing silicone, that causes the cure,they have no issue with section thickness. Indeed, they areadvantageously used for applications such as potting, encapsulating andlarge castings. Addition curing type organopolysiloxane compositions donot release reaction by-products so they can cure in closedenvironments. Their cure can also be greatly accelerated by heat curinghowever curing can be easily obtained without the need of heat, so atambient temperature 20° C. (+/−5° C.), by adjusting the level ofinhibitor and/or catalyst which is a great advantage compared toperoxide curing which needs temperature above 90° C.

According to another preferred embodiment, the addition curing typeorganopolysiloxane composition X comprises:

-   -   a) at least one organopolysiloxane A having at least two alkenyl        groups bonded to silicon per molecule, said alkenyl groups each        containing from 2 to 14 carbon atoms, preferably said alkenyl        groups are chosen from the group consisting of vinyl, allyl,        hexenyl, decenyl and tetradecenyl, and most preferably said        alkenyl groups are vinyl groups,    -   b) at least one silicon compound B having at least two and        preferably at least three hydrogen atoms bonded to silicon per        molecule,    -   c) hollow glass beads D, and preferably hollow borosilicate        glass microspheres,    -   d) a hydrosilylation catalyst C,    -   e) optionally at least one cure rate controller G which slows        the curing rate of the silicone composition,    -   f) optionally at least one reactive diluent E which reacts        through hydrosilylation reaction, and    -   g) optionally at least one additive H such as a pigment, a dye,        clays, a surfactant, hydrogenated castor oil, wollastonite,        aluminium trihydrate, magnesium hydroxide, halloysite, huntite        hydromagnesite, expandable graphite, zinc borate, mica or a        fumed silica.

According to another preferred embodiment, the addition curing typeorganopolysiloxane composition X comprises:

-   -   a) at least one organopolysiloxane A of the following formula:

-   -   -   in which:            -   R and R″, are chosen independently of one another from                the group consisting of C₁ to C₃₀ hydrocarbon radical,                and preferably R and R are an alkyl group chosen from                the group consisting of methyl, ethyl, propyl,                trifluoropropyl, and phenyl, and most preferably R is a                methyl group,            -   R′ is a C₁ to C₂₀ alkenyl radical, and preferably R′ is                chosen from the group consisting of vinyl, allyl,                hexenyl, decenyl and tetradecenyl, and most preferably                R′ is a vinyl radical, and            -   n is an integer having a value from 5 to 1000, and                preferably from 5 to 100,

    -   b) at least one silicon compound B comprising at least two        hydrogen atoms bonded to silicon per molecule, and preferably a        mixture of two silicon compounds B one comprising two telechelic        hydrogen atoms bonded to silicon per molecule with no pendent        hydrogen atoms bonded to silicon per molecule and the other        comprising at least three hydrogen atoms bonded to silicon per        molecule,

    -   c) an effective amount of hydrosilylation catalyst C, and        preferably a platinum based hydrosilylation catalyst C.

    -   d) hollow glass beads D, and preferably hollow borosilicate        glass microspheres,

    -   e) eventually and preferably at least one reactive diluent E for        reducing the viscosity of the composition and which reacts        through hydrosilylation reaction and is chosen from the group        consisting of:        -   a silicon compound comprising a single silicon hydride group            per molecule, and        -   an organic compound containing a single ethylenically            unsaturated group, preferably said organic compound is an            organic α-olefin containing from 3 to 20 carbon atoms, and            most preferably chosen from the group consisting of            dodecene, tetradecene, hexadecene, octadecene and a            combination of these and all with a terminal vinyl group,        -   an organopolysiloxane having a single telechelic alkenyl            group, and preferably said telechelic alkenyl group is            chosen from the group consisting of vinyl, allyl, hexenyl,            decenyl and tetradecenyl, and most preferably is a vinyl            group,

    -   f) optionally at least one additives H such as a pigment, a dye,        clays, a surfactant, hydrogenated castor oil, wollastonite,        aluminium trihydrate, magnesium hydroxide, halloysite, huntite        hydromagnesite, expandable graphite, zinc borate, mica or a        fumed silica, and

    -   g) optionally at least one cure rate controller G which slows        the curing rate of the silicone composition.

According to another preferred embodiment, the reactive diluent E:

-   -   is chosen from the group consisting of dodecene, tetradecene,        hexadecene, octadecene or a combination of these and all having        a terminal vinyl group, or    -   is a liquid organopolysiloxane with formula I

In which:

-   -   R are R², are chosen independently of one another from a C₁ to        C₃₀ hydrocarbon radical, and preferably they are chosen from the        group consisting of methyl, ethyl, propyl, trifluoropropyl and        phenyl, and most preferably are methyl groups,    -   R¹ is a C₁ to C₂₀ alkenyl radical, and preferably R¹ is chosen        from the group consisting of vinyl, allyl, hexenyl, decenyl, or        tetradecenyl, and most preferably R¹ is vinyl, and    -   x is between 0 and 100, and is chosen so that it will lower the        viscosity of addition curing type organopolysiloxane composition        X compared to same composition without the reactive diluent.

According to a preferred embodiment organopolysiloxane A is chosen fromthe group of dimethylpolysiloxanes containing dimethylvinylsilyl endgroups.

According to another preferred embodiment, wherein:

-   -   the viscosity at 25° C. of said organopolysiloxane A is between        5 mPa·s and 60000 mPa·s; and preferably between 5 mPa·s and 5000        mPa·s, and most preferably between 5 mPa·s and 350 mPa·s,    -   the viscosity at 25° C. of said silicon compound B comprising        two telechelic hydrogen atoms bonded to silicon per molecule        with no pendent hydrogen atoms bonded to silicon per molecule is        between 5 and 100 mPa·s, and    -   the viscosity at 25° C. of said silicon compound B comprising at        least three hydrogen atoms bonded to silicon per molecule is        between 5 and 2000 mPa·s.

All the viscosities under consideration in the present specificationcorrespond to a dynamic viscosity magnitude that is measured, in amanner known per se, at 25° C., with a machine of Brookfield type. Asregards to fluid products, the viscosity under consideration in thepresent specification is the dynamic viscosity at 25° C., known as the“Newtonian” viscosity, i.e. the dynamic viscosity that is measured, in amanner known per se, at a sufficiently low shear rate gradient so thatthe viscosity measured is independent of the rate gradient.

According to a preferred embodiment, the viscosities at 25° C. of saidorganopolysiloxane A and said silicon compound B comprising at least twohydrogen atoms bonded to silicon per molecule are chosen so that theviscosity at 25° C. of the addition curing type organopolysiloxanecomposition X is between 500 mPa-s and 300,000 mPa-s. so that it can beinjected into the battery module casing 102. If the option of pouringthe composition within the battery module casing 102 is chosen, then thecomponents of said addition curing type organopolysiloxane composition Xare chosen so that its viscosity is between 500 mPa·s to 5000 mPa·s andmost preferably between 500 mPa·s to 2500 mPa·s.

Examples of hydrosilylation catalysts C are hydrosilylation catalystssuch as Karstedt's catalyst shown in U.S. Pat. No. 3,715,334 or otherplatinum or rhodium catalysts known to those in the art, and alsoincluding microencapsulated hydrosilylation catalysts for example thoseknown in the art such as seen in U.S. Pat. No. 5,009,957. However,hydrosilylation catalysts pertinent to this invention can contain atleast one of the following elements: Pt, Rh, Ru, Pd, Ni, e.g. RaneyNickel, and their combinations. The catalyst is optionally coupled to aninert or active support. Examples of preferred catalysts which can beused include platinum type catalysts such as chloroplatinic acid,alcohol solutions of chloroplatinic acid, complexes of platinum andolefins, complexes of platinum and1,3-divinyl-1,1,3,3-tetramethyldisiloxane and powders on which platinumis supported, etc. The platinum catalysts are fully described in theliterature. Mention may in particular be made of the complexes ofplatinum and of an organic product described in U.S. Pat. Nos.3,159,601, 3,159,602 and 3,220,972 and European Patents EP-A-057,459,EP-188,978 and EP-A-190,530 and the complexes of platinum and ofvinylated organopolysiloxane described in U.S. Pat. Nos. 3,419,593,3,715,334, 3,377,432, 3,814,730, and 3,775,452, to Karstedt. Inparticular, platinum type catalysts are especially desirable.

Examples of cure rate controller G, which are also known as inhibitor,designed to slow the cure of the compounded silicone if needed. Curerate controllers are well known in the art and examples of suchmaterials can be found in U.S. Pat. No. 3,923,705 refers to the use ofvinyl contained cyclic siloxanes. U.S. Pat. No. 3,445,420 describes theuse of acetylenic alcohols. U.S. Pat. No. 3,188,299 shows theeffectiveness of heterocyclic amines. U.S. Pat. No. 4,256,870 describesalkyl maleates used to control cure. Olefinic siloxanes can also be usedas described in U.S. Pat. No. 3,989,667. Polydiorganosiloxanescontaining vinyl radicals have also been used and this art can be seenin U.S. Pat. Nos. 3,498,945, 4,256,870, and 4,347,346. Preferredinhibitors for this composition are methylvinylcyclosiloxanes,3-methyl-1-butyn-3-ol, and 1-ethynyl-1-cyclohexanol with the mostpreferred being the1,3,5,7-tetramethyl-1,3,5,7-tetravinyl-cyclotetrasiloxane in amountsfrom 0.002% to 1.00% of the silicone compound depending on the cure ratedesired.

The preferred cure rate controller G is chosen among:

-   1,3,5,7-tetramethyl-1,3,5,7-tetravinyl-cyclotetrasiloxane.-   3-methyl-1-butyn-3-ol, and-   1-ethynyl-1-cyclohexanol.

To obtain a longer working time or “pot life”, the quantity of the curerate controller G is adjusted to reach the desired “pot life”. Theconcentration of the catalyst inhibitor in the present siliconecomposition is sufficient to retard curing of the composition at ambienttemperature without preventing or excessively prolonging cure atelevated temperatures. This concentration will vary widely depending onthe particular inhibitor used, the nature and concentration of thehydrosilylation catalyst, and the nature of theorganohydrogenopolysiloxane. Inhibitor concentrations as low as one moleof inhibitor per mole of platinum group metal will in some instancesyield a satisfactory storage stability and cure rate. In otherinstances, inhibitor concentrations of up to 500 or more moles ofinhibitor per mole of platinum group metal may be required. The optimumconcentration for a particular inhibitor in a given silicone compositioncan be readily determined by routine experimentation.

According to a preferred embodiment, for said addition curing typeorganopolysiloxane composition X the proportions in weight of theorganopolysiloxane A, the reactive diluent E, when it is present, andthe silicon compound B are such that the overall molar ratio of thehydrogen atoms bonded to the silicon to the overall alkenyl radicalsbonded to the silicon is within a range from 0.35 to 10, and preferablywithin a range from 0.4 to 1.5.

Some additives H such as a pigment, a dye, clays, a surfactant,hydrogenated castor oil, wollastonite or a fumed silica (which modifythe flow of the compounded silicone product) can also be used withinsaid addition curing type organopolysiloxane composition X.

By “dye” it is meant a colored or fluorescent organic substance only,which impart color to a substrate by selective absorption of light. By“pigment” it is meant a colored, black, white or fluorescent particulateorganic or inorganic solids which usually are insoluble in, andessentially physically and chemically unaffected by, the vehicle orsubstrate in which they are incorporated. It alters appearance byselective absorption and/or by scattering of light. A pigment generallyretains a crystal or particulate structure throughout the colorationprocess. Pigments and dyes are well known in the art and need not bedescribed in detail herein.

Clays are products that are already well known per se, which aredescribed, for example, in the publication “Mineralogie des argiles[Mineralogy of clays], S. Caillere, S. Henin, M. Rautureau, 2nd Edition1982, Masson”. Clays are silicates containing a cation that may bechosen from calcium, magnesium, aluminium, sodium, potassium and lithiumcations, and mixtures thereof. Examples of such products that may bementioned include clays of the smectite family such as montmorillonites,hectorites, bentonites, beidellites and saponites, and also of thevermiculite, stevensite and chlorite families. These clays may be ofnatural or synthetic origin. The clay is preferably a bentonite or ahectorite, and these clays may be modified with a chemical compoundchosen from quaternary amines, tertiary amines, amine acetates,imidazolines, amine soaps, fatty sulfates, alkyl aryl sulfonates andamine oxides, and mixtures thereof. Clay which can be used according tothe invention, of synthetic hectorites (also known as laponites), suchas the products sold by Laporte under the name Laponite XLG, Laponite RDand Laponite RDS (these products are sodium magnesium silicates and inparticular lithium magnesium sodium silicates); bentonites, such as theproduct sold under the name Bentone HC by Rheox; magnesium aluminiumsilicates, in particular hydrated, such as the product sold by R.T.Vanderbilt Company under the name Veegum Ultra, or calcium silicates andin particular that in synthetic form sold by the company CELITE ET WALSHASS under the name Micro-Cel C.

Many silicone polyether surfactants are available, but a preferredsilicone polyether for thickening a silicone compound of this inventionwould be SP 3300 from Elkem Silicones USA.

Another preferred additive H is a rheology modifier such as Thixcin R, ahydrogenated castor oil, from Elementis Specialties, New Jersey, USA.

Wollastonite, also known as calcium metasilicate, is a naturallyoccurring mineral could be added as a flame retardant (quantities addedwill varies according to the application and will range between 1 partby weight to 15 parts by weight based on 100 parts by weight of theaddition curing type organopolysiloxane composition X. The wollastonitewhich could be used in this invention is a mined form, having anacicular morphology, that is a needle-like shape. Preferred wollastonitegrades are selected from materials supplied by NYCO® Minerals, Inc.,Willsboro N.Y.

Aluminium trihydrate (ATH) is a common flame retardant filler. Itdecomposes when heated above 180-200° C. at which point it absorbs heatand releases water to quench the flame. Magnesium hydroxide (MDH) has ahigher thermal stability than ATH. Endothermic (heat absorbing)decomposition starts at 300° C. whereupon water is released which couldact as a fire retardant.

Huntite/Hydromagnesite blends (Mg₃Ca(CO₃)₄/Mg₅(CO₃)₄(OH)₂·4H₂O). Huntiteand hydromagnesite occur, almost invariably, as mixtures in nature. Thehydromagnesite starts to decompose between 220° C. (open air) and 250°C. (under pressure in an extruder), which is high enough so that it canbe used as a flame retardant. The hydromagnesite gives off water andabsorbs heat, much like ATH and MDH do. In contrast, the huntitedecomposes above 400° C., absorbing heat but liberating carbon dioxide.

Fumed silicas can also be used as additive H for changing the rheologyof these materials. Fumed silicas can be obtained by high-temperaturepyrolysis of a volatile silicon compound in an oxyhydrogen flame,producing a finely divided silica. This process makes it possible inparticular to obtain hydrophilic silicas which have a large number ofsilanol groups at their surface which would tend to thicken a siliconecomposition more than silica with low levels of silanol. Suchhydrophilic silicas are sold for example under the names Aerosil 130,Aerosil 200, Aerosil 255, Aerosil 300 and Aerosil 380 by Degussa andCab-O-Sil HS-5, Cab-O-Sil EH-5, Cab-O-Sil LM-130, Cab-O-Sil MS-55 andCab-O-Sil M-5 by Cabot. It is possible to chemically modify the surfaceof the said silica via a chemical reaction which brings about areduction in the number of silanol groups. It is possible in particularto replace silanol groups with hydrophobic groups: a hydrophobic silicais then obtained. The hydrophobic groups can be:

-   -   trimethylsiloxyl groups, which are obtained in particular by        treating fumed silica in the presence of hexamethyldisilazane.        Silicas thus treated are known as “Silica silylate” according to        the CTFA (6th edition, 1995). They are sold for example under        the references Aerosil R812 by Degussa and Cab-O-Sil TS-530 by        Cabot, or    -   dimethylsilyloxyl or polydimethylsiloxane groups, which are        obtained in particular by treating fumed silica in the presence        of polydimethylsiloxane, or methyldichlorosilane.

Silicas thus treated are known as “Silica dimethyl silylate” accordingto the CTFA (6th edition, 1995). They are sold for example under thereferences Aerosil R972 and Aerosil R974 by Degussa, and Cab-O-SilTS-610 and Cab-O-Sil TS-720 by Cabot. The fumed silica preferably has aparticle size that may be nanometric to micrometric, for example rangingfrom about 5 to 200 nm.

According to another preferred embodiment said addition curing typeorganopolysiloxane composition X is stored before use as amulti-component RTV comprising at least two separate packages which arepreferably airtight, whereas the hydrosilylation catalyst C is notpresent in the same package with silicon compound B or with reactivediluent E when it is present and when it is a silicon compoundcomprising a single silicon hydride group per molecule.

According to another preferred embodiment said addition curing typeorganopolysiloxane composition X is stored before use as amulti-component RTV comprising at least two separate packages which arepreferably airtight:

-   -   a) the first package A1 comprising:        -   100 parts by weight of at least one organopolyiloxane A            according to the invention and as defined above,        -   from 5 to 30 parts by weight of hollow glass beads D            according to the invention and as defined above, and        -   from 0 to 30 parts and preferably from 5 to 30 parts by            weight of at least one reactive diluent E according to the            invention and as defined above, and        -   from 4 to 150 ppm based on metal platinum of a platinum            based hydrosilylation catalyst C.    -   b) the second package A2 comprising:        -   100 parts by weight of at least one organopolysiloxane A            according to the invention and as defined above,        -   from 10 to 70 parts by weight of a silicon compounds B one            comprising two telechelic hydrogen atoms bonded to silicon            per molecule according to the invention and as defined            above,        -   from 5 to 25 parts by weight of a silicon compounds B            comprising at least three hydrogen atoms bonded to silicon            per molecule according to the invention and as defined            above,        -   from 5 to 30 parts by weight of hollow glass beads D            according to the invention and as defined above, and        -   an effective amount of at least one cure rate controller G            which slows the curing rate.

Another object of the invention relates to a process for preparation ofa secondary battery pack according to the invention and as describedabove comprising the steps of:

-   -   a) preparing at least one battery module casing 102 in which is        disposed a plurality of battery cells 103 which are electrically        connected to one another,    -   b) introducing into the said battery module casing 102 the        addition curing type organopolysiloxane composition X as defined        in claim 3 or 11,    -   c) filling completely or partially said battery module casing        102, and    -   d) allowing the curing to occur so as to form a silicone rubber        syntactic foam comprising a silicone rubber binder and hollow        glass beads, and optionally    -   e) covering the battery module casing 102 with a lid.

A preferred embodiment of the above process according to the inventionrelates to the preparation of the addition curing typeorganopolysiloxane composition X comprising the steps of:

-   -   a) feeding into a base feed line a liquid silicone base MS1        comprising:        -   i) at least one organopolysiloxane A having at least two            alkenyl groups bonded to silicon per molecule, said alkenyl            groups each containing from 2 to 14 carbon atoms, preferably            said alkenyl groups are chosen from the group consisting of            vinyl, allyl, hexenyl, decenyl and tetradecenyl, and most            preferably said alkenyl groups are vinyl groups,        -   ii) hollow glass beads D, and preferably hollow borosilicate            glass microspheres D1,        -   iii) at least one silicon compound B having at least two and            preferably at least three hydrogen atoms bonded to silicon            per molecule, and        -   iv) optionally a cure rate controller G which slows the            curing rate,    -   b) feeding into a catalyst feed line a catalyst master batch MC        comprising:        -   i) at least one hydrosilylation catalyst C; and        -   ii) optionally, at least one organopolysiloxane A having at            least two alkenyl groups bonded to silicon per molecule,            said alkenyl groups each containing from 2 to 14 carbon            atoms, preferably said alkenyl groups are chosen from the            group consisting of vinyl, allyl, hexenyl, decenyl and            tetradecenyl, and most preferably said alkenyl groups are            vinyl groups;    -   c) feeding into an inhibitor feed line an inhibitor master batch        MI comprising:        -   i) a cure rate controller G which slows the curing rate; and        -   ii) optionally, at least one organopolysiloxane A having at            least two alkenyl groups bonded to silicon per molecule,            said alkenyl groups each containing from 2 to 14 carbon            atoms, preferably said alkenyl groups are chosen from the            group consisting of vinyl, allyl, hexenyl, decenyl and            tetradecenyl, and most preferably said alkenyl groups are            vinyl groups; and    -   d) optionally feeding into an additive feed line an additive        masterbatch MA comprising:        -   i) at least one additive H such as a pigment, a dye, clays,            a surfactant, hydrogenated castor oil, wollastonite,            aluminium trihydrate, magnesium hydroxide, halloysite,            huntite, hydromagnesite, expandable graphite, zinc borate,            mica or a fumed silica, and        -   ii) optionally at least one organopolysiloxane A having at            least two alkenyl groups bonded to silicon per molecule,            said alkenyl groups each containing from 2 to 14 carbon            atoms, preferably said alkenyl groups are chosen from the            group consisting of vinyl, allyl, hexenyl, decenyl and            tetradecenyl, and most preferably said alkenyl groups are            vinyl groups; and    -   e) directing said liquid silicone base MS1, said catalyst master        batch MC and said inhibitor master batch MI and optionally said        additive masterbatch MA into a tank to obtain the addition        curing type organopolysiloxane composition X.

The first advantage of said preferred embodiment relies on that thereaction rate of the crosslinking for the addition curing typeorganopolysiloxane composition X is regulated by the addition of a curerate controller G. As the addition of this essential component is donevia using a specific feed line, the level of inhibitor can be easilymodified by the operator which allows him to increase the rate of cureor reduce the temperature at which rapid curing will begin. This is akey advantage as the configuration of the newly designed secondarybattery packs involve more and more complex shapes which implies toadjust with caution on a case by case the curing rate.

The second main advantage relies that it is now possible to reduce thelevel of inhibitor and so to reduce the temperature at which rapidcuring begins. This can be important if there are components within thebattery pack that are somewhat temperature sensitive.

A preferred embodiment of the above process according to the inventionrelates to the preparation of the addition curing typeorganopolysiloxane composition X comprising the steps of:

-   -   a) feeding into a base feed line a liquid silicone base MS2        comprising:        -   i) at least one organopolysiloxane A having at least two            alkenyl groups bonded to silicon per molecule, said alkenyl            groups each containing from 2 to 14 carbon atoms, preferably            said alkenyl groups are chosen from the group consisting of            vinyl, allyl, hexenyl, decenyl and tetradecenyl, and most            preferably said alkenyl groups are vinyl groups, and        -   ii) at least one silicon compound B having at least two and            preferably at least three hydrogen atoms bonded to silicon            per molecule,        -   iii) optionally a cure rate controller G which slows the            curing rate,    -   b) feeding into a catalyst feed line a catalyst master batch MC        comprising:        -   i) at least one hydrosilylation catalyst C; and        -   ii) optionally, at least one organopolysiloxane A having at            least two alkenyl groups bonded to silicon per molecule,            said alkenyl groups each containing from 2 to 14 carbon            atoms, preferably said alkenyl groups are chosen from the            group consisting of vinyl, allyl, hexenyl, decenyl and            tetradecenyl, and most preferably said alkenyl groups are            vinyl groups;    -   c) feeding into an inhibitor feed line an inhibitor master batch        MI comprising:        -   i) a cure rate controller G which slows the curing rate; and        -   ii) optionally, at least one organopolysiloxane A having at            least two alkenyl groups bonded to silicon per molecule,            said alkenyl groups each containing from 2 to 14 carbon            atoms, preferably said alkenyl groups are chosen from the            group consisting of vinyl, allyl, hexenyl, decenyl and            tetradecenyl, and most preferably said alkenyl groups are            vinyl groups; and    -   d) optionally feeding into an additive feed line an additive        masterbatch MA comprising:        -   i) at least one additive H such as a pigment, a dye, clays,            a surfactant, hydrogenated castor oil, wollastonite,            aluminium trihydrate, magnesium hydroxide, halloysite,            huntite hydromagnesite, expandable graphite, zinc borate,            mica or a fumed silica, and        -   ii) optionally at least one organopolysiloxane A having at            least two alkenyl groups bonded to silicon per molecule,            said alkenyl groups each containing from 2 to 14 carbon            atoms, preferably said alkenyl groups are chosen from the            group consisting of vinyl, allyl, hexenyl, decenyl and            tetradecenyl, and most preferably said alkenyl groups are            vinyl groups;    -   e) directing said liquid silicone base MS2, said catalyst master        batch MC and said inhibitor master batch MI and optionally said        additive masterbatch MA into a stirring tank; and    -   f) operating said stirring tank, thereby mixing said liquid        silicone base MS1, said catalyst master batch MC and said        inhibitor master batch MI and optionally said additive        masterbatch MA preferably by using a high flow, low-shear mixer,        and    -   g) adding hollow glass beads D and preferably hollow        borosilicate glass microspheres D1 into said stirring tank,        preferably by means using gravity discharge or screw feeder to        obtain the addition curing type organopolysiloxane composition        X.

All the components of the preferred embodiments of the preparation ofthe addition curing type organopolysiloxane composition X have beenalready described above.

According to a preferred embodiment, the secondary battery packaccording to the invention is located within a vehicle.

It is understood that the term “vehicle” as used herein is inclusive ofmotor vehicles in general such as passenger automobiles including sportsutility vehicles (SUV), buses, trucks, various commercial vehicles,watercraft including a variety of boats and ships, aircraft, and thelike, and includes hybrid vehicles, electric vehicles, plug-in hybridelectric vehicles, hydrogen-powered vehicles and other alternative fuelvehicles (e.g., fuels derived from resources other than petroleum). Asreferred to herein, a hybrid vehicle is a vehicle that has two or moresources of power, for example both gasoline-powered and electric-poweredvehicles.

In another preferred embodiment, the secondary battery pack according tothe invention is located in an automotive motor vehicle.

In another embodiment, the secondary battery pack according to theinvention is located in an all-electric vehicle (EV), a plug-in hybridvehicle (PHEV), a hybrid vehicle (HEV).

In another embodiment, the secondary battery pack according to theinvention is located in: an aircraft, a boat, a ship, a train or wallunit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a top view of a secondary battery pack without a lidwith batteries inside the pack;

FIG. 2 provides a perspective view of a secondary battery pack withbatteries inside the pack;

FIG. 3 provides a top view of batteries in a secondary battery pack withsilicone rubber syntactic foam according to the invention filling thespace between batteries and the remaining space in the pack;

FIG. 4 provides a top view of battery cells in a secondary battery packcovered with silicone rubber syntactic foam according to the inventionand with said foam filling the space between batteries and the remainingspace in the pack;

FIGS. 5 and 6 provide a schematic representation of two preferredembodiments of a method for producing an addition curing typeorganopolysiloxane composition X wherein the inhibitor master batch MIand catalyst master batch MC are separately fed into other components soas to control the curing rate.

FIGS. 1 and 2 show that battery cells 103 can be very close together ina battery module casing 102. In one embodiment of the invention acrosslinkable silicone composition according to the invention andprecursor of a lightweight silicone rubber syntactic foam comprising asilicone rubber binder and hollow glass beads is poured into the batterymodule casing 102 after the batteries have been placed and installed(FIG. 3, 104 ) and yield to a silicone syntactic foam when it is cured(FIG. 4, 105 ).

FIG. 5 shows a method for producing an addition curing typeorganopolysiloxane composition X according to one embodiment of theinvention wherein said liquid silicone base MS1 is stored in a storagetank 1, said catalyst master batch MC is stored in a storage tank 20,said inhibitor master batch MI is stored in a storage tank 50 and saidadditive masterbatch MA is stored in a storage tank 65 and are fedseparately into their respective feed lines 200, 210, 220 and 230respectively. The storage tank 1 of the liquid silicone base MS2 isconnected to the stirring tank 80 via a feed pump 10, which can be anylarge displacement pump, and via an optional feed rate adjuster 15. Thestorage tank 20 of the catalyst master batch MC is connected to thestirring tank 80 via a feed pump 25, which can be any small pistondisplacement pump, gear pump, micro motion injector pump, or otherpositive displacement pump, and via an optional feed rate adjuster 30.The storage tank 50 of the inhibitor master batch MI is connected to thestirring tank 80 via a feed pump 55, which can be any small pistondisplacement pump, gear pump, micro motion injector pump, or otherpositive displacement pump, and via an optional feed rate adjuster 60.The storage tank 65 of the additive masterbatch MA is connected to thestirring tank 80 via a feed pump 70, which can be any small pistondisplacement pump, gear pump, micro motion injector pump, or otherpositive displacement pump, and via an optional feed rate adjuster 75.When said liquid silicone base MS2, said catalyst master batch MC andsaid inhibitor master batch MI and optionally said additive masterbatchMA are directed into said stirring tank 80; the resulting mixture ismixed preferably by using a high flow, low-shear mixer to yield theaddition curing type organopolysiloxane composition X according to theinvention. Said composition is now available to be introduced into thesaid battery module casing 102 by mean 100 which could be either via aninjection apparatus or via a pump to allow free flow to fill the freespaces of battery module casing 102 and cures via crosslinking.

FIG. 6 shows a method for producing an addition curing typeorganopolysiloxane composition X according to another embodiment of theinvention wherein said liquid silicone base MS2 is stored in a storagetank 1, said catalyst master batch MC is stored in a storage tank 20,said inhibitor master batch MI is stored in a storage tank 50 and saidadditive masterbatch MA is stored in a storage tank 65 and are fedseparately into their respective feed lines 200, 210, 220 and 230respectively. The storage tank 1 of the liquid silicone base MS2 isconnected to the stirring tank 80 via a feed pump 10, which can be anylarge displacement pump, and via an optional feed rate adjuster 15. Thestorage tank 20 of the catalyst master batch MC is connected to thestirring tank 80 via a feed pump 25, which can be any small pistondisplacement pump, gear pump, micro motion injector pump, or otherpositive displacement pump, and via an optional feed rate adjuster 30.The storage tank 50 of the inhibitor master batch MI is connected to thestirring tank 80 via a feed pump 55, which can be any small pistondisplacement pump, gear pump, micro motion injector pump, or otherpositive displacement pump, and via an optional feed rate adjuster 60.The storage tank 65 of the additive masterbatch MA is connected to thestirring tank 80 via a feed pump 70, which can be any small pistondisplacement pump, gear pump, micro motion injector pump, or otherpositive displacement pump, and via an optional feed rate adjuster 75.When said liquid silicone base MS2, said catalyst master batch MC andsaid inhibitor master batch MI and optionally said additive masterbatchMA are directed into said stirring tank 80; the resulting mixture ismixed preferably by using a high flow, low-shear mixer. To saidresulting mixture, hollow glass beads D and preferably hollowborosilicate glass microspheres D1 which are stored in storage tank 90,which is preferably a hopper, are transferred into said stirring tank 80either directly by gravity discharge or via screw feeder 95 to yieldaddition curing type organopolysiloxane composition X according to theinvention. Said composition is now available to be introduced into thesaid battery module casing 102 by mean 100 which could be either via aninjection apparatus or via a pump to allow free flow to fill the freespaces of battery module casing 102 and cures via crosslinking.

Other advantages provided by the present invention will become apparentfrom the following illustrative examples.

EXAMPLES I) Definition of the Components

Organopolysiloxane A1=polydimethylsiloxane with dimethylvinylsilylend-units with a viscosity at 25° C. ranging from 80 mPa·s to 120 mPa·s;

Organopolysiloxane A2=polydimethylsiloxane with dimethylvinylsilylend-units with a viscosity at 25° C. ranging from 500 mPa·s to 650mPa·s;

Organopolysiloxane B1 (CE) as chain extender=polydimethylsiloxane withdimethylsilylhydride end-units with a viscosity at 25° C. ranging from 7mPa·s to 10 mPa·s and formula: M′D_(x)M′

In which:

-   -   D is a siloxy unit of formula (CH₃)₂SiO_(2/2)    -   M′ is a siloxy unit of formula (CH₃)₂(H)SiO₂    -   and x is an integer ranging from 8 to 11;

Organopolysiloxane B2 (XL) as crosslinker, with a viscosity at 25° C.ranging from 18 mPa·s to 26 mPa·s, over 10 SiH reactive groups arepresent (in average from 16 to 18 SiH reactive groups):poly(methylhydrogeno) (dimethyl)siloxane with SiH groups in-chain andend-chain (α/ω),

Hollow glass beads D1: 3M™ Glass Bubbles Series S15, sold by 3M Company,Particle Size (50%) microns by volume=55 microns, Isostatic CrushStrength: Test Pressure 300 psi (2.07 MPa.), True Density (g/cc)=0.15.

Hollow glass beads D2: 3M™ Glass Bubbles Series K25, sold by 3M Company,(Particle Size (50%) microns by volume=55 microns, Isostatic CrushStrength Test Pressure 750 psi, True Density (g/cc)=0.25.

Cure rate controller G1:1,3,5,7-tetramethyl-1,3,5,7-tetravinyl-cyclotetrasiloxane.

Cure rate controller G2: 1-Ethynyl-1-cyclohexanol (ECH).

Catalyst C: 10% platinum as Karstedt catalyst in 350 cSdimethylvinyldimer, sold by Johnson Matthey Company.

Reactive diluent E=1-tetradecene.

II) Examples Part I

TABLE 1 Inventive two-parts formulation 1 precursor of a silicone rubbersyntactic foam Parts by weight Part A Organopolysiloxane A1 81.88Reactive diluent E 5.03 Catalyst C 0.037 hollow glass beads D1 13.05Part B Organopolysiloxane A1 81.88 Organopolysiloxane B2 (XL) 8.6Organopolysiloxane B1 (CE) 53.41 Cure rate controller G1 0.01 hollowglass beads D1 13.05

TABLE 2 Inventive two-parts formulation 2 precursor of a silicone rubbersyntactic foam. Parts by weight Part A Organopolysiloxane A1 78.27Reactive diluent E 8.62 Catalyst C 0.063 hollow glass beads D1 13.05Part B Organopolysiloxane A1 69.23 Organopolysiloxane B2 (XL) 2.46Organopolysiloxane B1 (CE) 15.26 Cure rate controller G1 0.0029 hollowglass beads D1 13.05

-   -   For two-parts formulation 1, parts A and B were combined as a        6:1 w/w (weight ratio) to prepare the compositions I before        curing    -   For two-parts formulation 2, parts A and B were combined as a        1:1 w/w (weight ratio) to prepare the compositions II before        curing.

Each formulation 1 and 2 were poured before curing inside a batterymodule casing 102 in which was disposed a plurality of battery cells 103which were electrically conductively connected to one another. Thecuring occurred at room temperature to yield a rubber syntactic foamcomprising a silicone rubber binder and hollow glass beads which filledfully the open space of said battery module casing 102 and coveredtotally said battery cells 103.

III) Examples Part II

The following formulations were prepared:

TABLE 3 Formulation 3 - Comparative Percent by weight Part AOrganopolysiloxane A1 99.8% Catalyst C 0.2% Total 100.0% Part BOrganopolysiloxane A1 78.0749% Organopolysiloxane B1 (CE) 19.5550%Organopolysiloxane B2 (XL) 2.3689% Cure rate controller G2 0.0012% Total100.0000%

TABLE 4 Formulation 4 - Invention Percent by weight Part AOrganopolysiloxane A1 83.6900% Catalyst C 0.0335% Hollow glass beads D216.2800% Total 100.0035% Part B Organopolysiloxane A1 65.21%Organopolysiloxane B1 (CE) 16.69% Organopolysiloxane B2 (XL) 1.82%Hollow glass beads D2 16.28% Total 100.00%

TABLE 5 Formulation 5 - Invention Percent by weight Part AOrganopolysiloxane A1 80.0396% Catalyst C 0.1604% Hollow glass beads D219.8000% Total 100.0000% Part B Organopolysiloxane A1 62.6161%Organopolysiloxane B1 (CE) 15.6831% Organopolysiloxane B2 (XL) 1.8999%Cure rate controller G2 0.0010% Hollow glass beads D2 19.8000% Total100.0000%

-   -   Formulation 3 was mixed at 1:1 mix ratio by weight and cured at        room temperature (25° C.) overnight for 16 hours to yield a        cured silicone elastomer.    -   Formulations 4 to 7 were mixed at 1:1 mix ratio by weight and        cured at room temperature (25° C.) overnight for 16 hours to        yield silicone syntactic foams according to the inventions.    -   Formulation 8 was prepared by mixing at 1:1 mix ratio by weight        the two part component sold by Elkem Silicones under the        reference RTV-3040 (2 part component, polyaddition curing        system) and cured at room temperature (25° C.) overnight for 16        hours to yield a cured silicone elastomer.    -   Formulation 9 was prepared by mixing at 1:1 mix ratio by weight        the two part component sold by Elkem Silicones under the        reference Bluesil™ ESA 7242 (which is a two-component heat        curing liquid silicone elastomer that cross-links by a        polyaddition) and was cured at room temperature (25° C.)        overnight for 16 hours to yield a cured silicone elastomer.    -   Formulation 10 has been prepared based on Sakrete Concrete The        concrete used was from SAKRETE of North America, LLC located in        Charlotte, N.C. The product is called SAKRETE High Strength        Concrete Mix. The concrete sample was made using the following        process:        -   Pour 1 kg of the high strength concrete mix into a container            forming an indentation in the center of the concrete.        -   Enough water was added to obtain a workable mix (70 g).        -   Material was poured into a 51 mm diameter mold.        -   The material was worked into voids and then flattened with a            metal spatula.        -   The material was allowed to harden until a thumb print could            not be left in the material.        -   A metal spatula was used to obtain a desired finish and            flatness as the material was hardening.        -   The material was kept moist and underneath plastic for 7            days while constantly being kept at room temperature.

TABLE 8 Physical properties of the cured products Tensile StrengthSpecific Durometer Cured Samples psi Gravity Shore A Formulation 5(Invention) 40.0 0.55 80 Formulation 7 (Invention) 18.4 0.61 62Formulation 4 (Invention) 18.9 0.67 53 Formulation 6 (Invention) 16.10.55 59 Formulation 3 (Comparative) Gel Gel Gel Formulation 9(Comparative) 48.0 1.37 48

TABLE 9 Thermal conductivity measurement of cured samples. Bulk ThermalConductivity Cured sample (W/m · K) Formulation 5 (Invention) 0.1266Formulation 7 (Invention) 0.1240 Formulation 4 (Invention) 0.1274Formulation 6 (Invention) 0.1203 Formulation 3 (comparative) 0.1760Formulation 8 (comparative) 0.2280 Formulation 9 (comparative) 0.4261Formulation 10 (comparative) 1.9190

Thermal conductivity was measured using a Thermtest Hot Disk TPS(Transient Plane Source) 2500S Tester and are quoted in Table 9. Table 9shows that the example formulations according to the invention(Formulations 4 to 6) have lower thermal conductivity than thecomparative materials: formulation 8 (RTV 3040), formulation 9 (ESA7242), formulation 10 (Sakrete Concrete) and formulation 3 (ESA 7200).

It is an advantage to have a thermally insulating material. If a batteryor multiple batteries in the pack overheat, an insulating materialsurrounding the battery will help prevent excessive heat from reachingthe passenger area of an electric vehicle (car, truck, boat, train,plane, etc.).

Another advantage of the cured formulations 4 to 7 according to theinvention is that they can absorb vibration. Resilience is related tovibration. The more resilient a material is, the more vibration istranslated through the material. Using a Shore® Model SRI Resiliometer,commonly referred to as a Bayshore Resiliometer, to quickly andaccurately measure the “Rubber Property—Resilience by Vertical Rebound”as described in ASTM D2632. The resilience of example according to theinvention and comparative materials were measured and the results aredisclosed in Table 9. All the formulations were mixed at 1:1 mix ratioby weight and cured at room temperature overnight for 16 hours. A weightdrops on the test sample, and rebounds above the test sample when ithits the sample. When the weight hits the sample and bounces high, it ismore resilient. When the weight does not bounce as high, the material isless resilient.

TABLE 10 resilience measurement of some of the cured products.Resilience Cured sample Number of units Formulation 5 (Invention) 14Formulation 7 (Invention) 10 Formulation 4 (Invention) 10 Formulation 6(Invention) 13 Formulation 8 (comparative) 61 Formulation 9(comparative) 64

Table 10 shows that the comparative formulation have higher resilienceand will translate vibration through the materials more readily whereascured formulations according to the invention have lower resilience.

“Tan delta” is an abbreviated form of the terms “Tangent of Delta”. Thetan delta quantifies the way in which a material absorbs and dispersesenergy. It expresses the out-of-phase time relationship between animpact force and the resultant force that is transmitted to thesupporting body. The tan delta is also known as the Loss Factor due tothis loss of energy from the impact force via conversion to, anddispersal of, a safer form of energy. Thus, the tan delta is ultimatelyan indication of the effectiveness of a material's damping capabilities.The higher the tan delta, the greater the damping coefficient, the moreefficient the material will be in effectively accomplishing energyabsorption and dispersal. Tan delta is equal to the ratio of lossmodulus over the storage modulus or tan(delta)=G″/G′.

G″=loss modulus and G′=storage modulus. Higher values correlate to amaterial that dampens more effectively than those with lower values.Table 11 shows that the examples of the inventive materials dampenbetter than the comparative material.

TABLE 11 tan delta measurements of some of the cured products Tan DeltaCured sample Number of units Formulation 5 (Invention) 18.2679Formulation 7 (Invention) 17.7256 Formulation 4 (Invention) 24.1223Formulation 6 (Invention) 22.9557 Formulation 9 (comparative) 12.6070Formulation 10 (comparative) 8.7501

Tan delta measurements were made using an Anton Parr MCR 302 at 25° C.G″ and G′ were measured as the material cured. The tan delta wascalculated from these two values. The cured sample of the siliconesyntactic foams prepared from addition curing type organopolysiloxanescompositions according to a preferred embodiment of the invention couldbe advantageously used as damping material and fulfill the requiredtargeted goal within electric vehicle field which is looking eagerly toa damping control strategy to minimize drivetrain oscillations.

Flame resistance of 3 cured material according to the invention weremeasured and are quoted in Table 12. All formulations tested wereself-extinguishing.

TABLE 12 Flame resistance results of some cured material according tothe invention. Flame Burn Flame Bum Time Glow Time Time After After 2ndAfter 2nd 10 s Burn 10 s Burn 10 s Burn Cured Samples seconds secondsseconds Formulation 7 68.0 0.0 0.0 (Invention) Formulation 4 46.0 0.00.0 (Invention) Formulation 6 48.6 0.0 0.0 (Invention)

IV) Examples Part III

TABLE 13 Formulation 11 - Invention Percent by weight Part AOrganopolysiloxane A1 84.1263% Catalyst C 0.0337% Hollow glass beads D215.8400% Total 100.0000% Part B Organopolysiloxane A1 65.551%Organopolysiloxane B1 (CE) 16.778% Organopolysiloxane B2 (XL) 1.830%Cure rate controller G2 0.001% Hollow glass beads D2 15.840% Total100.000%

Formulation 11 (invention) and a comparative formulation 12 (tincatalyzed condensation cured product) are prepared according to theingredient described respectively in Tables 13 and 14.

TABLE 14 Formulation 12 - Condensation Cured Comparative Formulation 12Condensation Cured Comparative Formulation 12 Percent by weight*Dimethylsilanol α,ω-endblocked 70.16% polydimethylsiloxane with aviscosity of approximately 3500 mPa-s. Hollow glass beads D2 15.84% HiPro Green - Tin based cure catalyst 5.00% with alkoxy silanes for curingsilanol functional siloxane - Product is sold by Elkem Silicones USACorporation in York South Carolina USA Total 91.00%

Battery packs can have long distances that the insulating material (theliquid precursor, before crosslinking, of the silicone syntactic foamaccording to the invention) needs to travel from the outside air whenfilling the pack. The comparative formulation 12 described above needsmoisture from the air to cure quickly. The formulation was mixed at 25°C. and allowed to rest at that temperature until it had cured enough foran initial durometer reading could be taken. The condensation curablecomparative formulation 12 was also made and allowed to rest in the samefashion as the inventive formulation 11. Both samples were made and thenallowed to rest after being poured into an aluminum dish that hadmaterial at 1 cm thickness and 5.2 cm in diameter. One 5.2 cm face ofthe material was exposed to the air and no air (or moisture from theair) could move through the bottom or sides of the aluminum dish. Thisconfiguration is representative of what might happen in a typicalbattery pack. Air with moisture could be present over one face of thepotting material for a battery, while much of the material is below thatsurface relying on moisture to migrate through the bulk of the pottingmaterial.

Regarding inventive formulation 11 it took approximately 12 minutes tobe able to measure the durometer of the material on a Shore A range. Thedurometer was approximately 15 Shore A. At one hour the durometer was 50Shore A. Similar formulations reached approximately 52-54 Shore A inprevious examples. When checking the condensation curable formulation12, it took until 1 hour and 42 minutes before a durometer measurementcould be made, and the value was 11.7 Shore A. When pressing on thesample by hand, and then pulling a second sample (equivalent in a dish)apart, it was found that the bottom half of the sample was still liquid.The test sample was only cured in a layer on the top. This indicatesthat the condensation cured material requires significantly longer timeto cure in a representative test configuration than the inventiveformulation. It would be advantageous if the material cures more quicklyto speed up production times when potting battery packs.

Another cure system, a peroxide cure system was tested. However,peroxides typically require heat to cure so this is already adisadvantage. As shown above, the inventive formulation 11 can be madeto cure very quickly if that is desired, and no heat or energy to heatis required.

As below a peroxide comparative formulation 13 is described in Table 15:

TABLE 15 Formulation 13 - Peroxide Cured Comparative Formulation 1:1 MixRatio by weight Percent by weight Part A Hollow glass beads D2 15.84%Organopolysiloxane A2 84.16% Total 100.00% Part B Hollow glass beads D215.84% Organopolysiloxane A2 62.54% Organopolysiloxane A3 21.02% DBPH*0.61% Total 100.01% *DBPH = Varox ® = consist of greater than 90% byweight of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and is sold by R. T.Vanderbilt Organopolysiloxane A3: Poly(methylvinyl)(dimethyl)siloxanewith dimethylvinylsilyl end-units with a viscosity at 25° C. = 390 mPa ·s;

Class and Grasso suggest curing silicones with a DBPH catalyst at 177°C. for one hour (reference: Class, J. B.; Grasso, R. P., The Efficiencyof Peroxides for Curing Silicone Elastomers, Rubber Chemistry andTechnology, September 1993, Vol. 66, No. 4, pp. 605-622). We followedthis advice in curing our formulation as well. No post cure was done.

The same type of container was used to hold the material during cure(aluminum dish, one open face, 5.2 cm in diameter and 1 cm thickness ofthe poured material). We kept one face open, because when performingpotting, it is common to pour into a container and cure the materialopen to the air. Placing a lid on the container to keep air out would bean extra cost for the lid and extra time to attach the lid in aproduction setting. When cured for one hour at 177° C., the sample wasremoved from the oven. The surface facing the air was not cured. This isnot an unusual phenomenon, but was tested in these formulations to seeif a similar formulation to the inventive formulation would have theissues seen in other peroxide cured silicone formulations. Once theuncured layer was removed, the cured peroxide comparative elastomerformulation 13 had a durometer of 20 Shore A.

Three ways to eliminate lack of cure at an oxygen containing interfaceare typically used in the industry:

-   -   Removal of oxygen from the cure zone by use of inert gas, by use        of waxes that migrate to the surface and form a barrier, or by        use of films that are in direct contact with the coating.    -   Increasing free radical concentration by increasing the peroxide        level.    -   Use chemicals that react with the peroxy radicals.

All of these solutions to lack of cure may work. However, heating wouldstill be needed for the sample and implementation of the solutions wouldeither require much more complicated formulations which change the curedelastomer (i.e. waxes, chemicals that react with the peroxy radicals,etc.) and more expensive formulations (i.e. more free radicalperoxides).

1. A combination for preparation of a silicone rubber syntactic foam,wherein the silicone rubber syntactic foam comprises hollow glass beadsD, the combination comprising: (i) an organopolysiloxane A having atleast two alkenyl groups bonded to silicon per molecule, the alkenylgroups each containing from 2 to 14 carbon atoms, wherein theorganopolysiloxane A has a viscosity at 25° C. of about 5 mPa·s to about5,000 mPa·s; (ii) a silicon compound B comprising: (a) a silicon chainextender B1 having two telechelic hydrogen atoms bonded to silicon permolecule with no pendent hydrogen atoms bonded to silicon per molecule,wherein the viscosity at 25° C. of the silicon chain extender B1 isbetween about 5 and about 100 mPa·s; and (b) a silicon crosslinker B2having at least three hydrogen atoms bonded to silicon per molecule,wherein the viscosity at 25° C. of the silicon crosslinker B2 is betweenabout 5 and about 2000 mPa·s; (iii) a hydrosilylation catalyst C; (iv)optionally at least one cure rate controller G which slows the curingrate of the silicone foam combination; and (v) optionally at least oneadditive H, optionally the additive H comprises a pigment, a dye, clays,a surfactant, hydrogenated castor oil, wollastonite, aluminiumtrihydrate, magnesium hydroxide, halloysite, huntite hydromagnesite,expandable graphite, zinc borate, mica and/or a fumed silica; whereinthe proportions in weight of the organopolysiloxane A (i) and thesilicon compound B (ii) are such that the overall molar ratio of thehydrogen atoms bonded to the silicon to the overall alkenyl radicalsbonded to the silicon is between about 0.4 to about 1.5; and wherein,upon inclusion of between about 9% to about 20% by weight of the hollowglass beads D in the combination, the combination has a viscosity at 25°C. between about 500 mPa·s and about 5,000 mPa·s and is capable offilling a battery module casing.
 2. The combination of claim 1, whereinupon inclusion of between about 9% to about 20% by weight of the hollowglass beads D in the combination, the combination has a viscosity at 25°C. between about 500 mPa·s and about 2,500 mPa·s.
 3. The combination ofclaim 1, wherein when cured in the presence of the hollow glass beads D,the combination provides a silicone rubber syntactic foam that is flameresistant.
 4. The combination of claim 2, wherein when cured in thepresence of the hollow glass beads D, the combination provides asilicone rubber syntactic foam that is flame resistant.
 5. Thecombination of claim 1, wherein the silicon compound B (ii) has a weightratio of the silicon chain extender B1 to the silicon crosslinker B2from about 6.2:1 to about 11.2:1.
 6. The combination of claim 1, whereinthe silicon compound B (ii) has a weight ratio of the silicon chainextender B1 to the silicon crosslinker B2 from about 6.2:1 to about10.8:1.
 7. The combination of claim 1, wherein the silicon compound B(ii) has a weight ratio of the silicon chain extender B1 to the siliconcrosslinker B2 from about 6.2:1 to about 8.9:1.
 8. The combination ofclaim 1, wherein the at least two alkenyl groups bonded to silicon permolecule of the organopolysiloxane A is selected from the groupconsisting of vinyl, allyl, hexenyl, decenyl, tetradecenyl, andcombinations thereof.
 9. The combination of claim 1, wherein thehydrosilylation catalyst C is selected from the group consisting ofKarstedt's catalyst, platinum-based catalysts, rhodium-based catalysts,ruthenium-based catalysts, paladium-based catalysts, nickel-basedcatalysts, and combinations thereof.
 10. The combination of claim 1,wherein the optional cure rate controller G is selected from the groupconsisting of vinyl-containing cyclic siloxanes, acetylenic alcohols,heterocyclic amines, alkyl maleates, olefinic siloxanes,polydiorganosiloxanes containing vinyl radicals, and combinationsthereof.
 11. A combination for preparation of a silicone rubbersyntactic foam, where the silicone rubber syntactic foam compriseshollow glass beads D, the combination comprising: (i) anorganopolysiloxane A having at least two alkenyl groups bonded tosilicon per molecule, the alkenyl groups each containing from 2 to 14carbon atoms, wherein the organopolysiloxane A has a viscosity at 25° C.of about 5 mPa·s to about 5,000 mPa·s; (ii) a silicon compound Bcomprising: (a) a silicon chain extender B1 having two telechelichydrogen atoms bonded to silicon per molecule with no pendent hydrogenatoms bonded to silicon per molecule, wherein the viscosity at 25° C. ofthe silicon chain extender B1 is between about 5 and about 100 mPa·s;and (b) a silicon crosslinker B2 having at least three hydrogen atomsbonded to silicon per molecule, wherein the viscosity at 25° C. of thesilicon crosslinker B2 is between about 5 and about 2000 mPa·s; and(iii) a hydrosilylation catalyst C; and (iv) at least one cure ratecontroller G which slows the curing rate of the silicone foamcombination; wherein the proportions in weight of the organopolysiloxaneA (i) and the silicon compound B (ii) are such that the overall molarratio of the hydrogen atoms bonded to the silicon to the overall alkenylradicals bonded to the silicon is between about 0.4 to about 1.5; andwherein, upon inclusion of between about 9% to about 20% by weight ofthe hollow glass beads D in the combination, the combination has aviscosity at 25° C. between about 500 mPa·s and about 5,000 mPa·s and iscapable of filling a battery module casing.
 12. The combination of claim11, wherein upon inclusion of between about 9% to about 20% by weight ofthe hollow glass beads D in the combination, the combination has aviscosity at 25° C. between about 500 mPa·s and about 2,500 mPa·s. 13.The combination of claim 11, wherein when cured, the combinationprovides a silicone rubber syntactic foam that is flame resistant. 14.The combination of claim 12, wherein when cured, the combinationprovides a silicone rubber syntactic foam that is flame resistant. 15.The combination of claim 11, wherein the silicon compound B (ii) has aweight ratio of the silicon chain extender B1 to the silicon crosslinkerB2 from about 6.2:1 to about 11.2:1.
 16. The combination of claim 11,wherein the silicon compound B (ii) has a weight ratio of the siliconchain extender B1 to the silicon crosslinker B2 from about 6.2:1 toabout 10.8:1.
 17. The combination of claim 11, wherein the siliconcompound B (ii) has a weight ratio of the silicon chain extender B1 tothe silicon crosslinker B2 from about 6.2:1 to about 8.9:1.
 18. Thecombination of claim 11, wherein the at least two alkenyl groups bondedto silicon per molecule of the organopolysiloxane A is selected from thegroup consisting of vinyl, allyl, hexenyl, decenyl, tetradecenyl, andcombination thereof.
 19. The combination of claim 11, wherein thehydrosilylation catalyst C is selected from the group consisting ofKarstedt's catalyst, platinum-based catalysts, rhodium-based catalysts,ruthenium-based catalysts, paladium-based catalysts, nickel-basedcatalysts, and combinations thereof.
 20. The combination of claim 11,wherein the cure rate controller G is selected from the group consistingof vinyl-containing cyclic siloxanes, acetylenic alcohols, heterocyclicamines, alkyl maleates, olefinic siloxanes, polydiorganosiloxanescontaining vinyl radicals, and combinations thereof.
 21. A kit of partsfor preparation of a silicone rubber syntactic foam, wherein thesilicone rubber syntactic foam comprises hollow glass beads D, the kitcomprising two packages: the first package P1 comprising: 100 parts byweight of (i) an organopolysiloxane A, and from 4 to 150 ppm based onmetal platinum of a platinum-based hydrosilylation catalyst C; and thesecond package P2 comprising: 100 parts by weight of (i) where theorganopolysiloxane, from 10 to 70 parts by weight of a silicon chainextender B1, from 5 to 25 parts by weight of a silicon crosslinker B2,and optionally an effective amount of at least one cure rate controllerG (iv) which slows the curing rate; (i) wherein the organopolysiloxane Ahas at least two alkenyl groups bonded to silicon per molecule, thealkenyl groups each containing from 2 to 14 carbon atoms, and whereinthe organopolysiloxane A has a viscosity at 25° C. of from about 5 mPa·sto about 5,000 mPa·s; (ii) wherein the silicon chain extender B1 has twotelechelic hydrogen atoms bonded to silicon per molecule with no pendenthydrogen atoms bonded to silicon per molecule and a viscosity at 25° C.of from about 5 to about 100 mPa·s; and (iii) wherein the siliconcrosslinker B2 has at least three hydrogen atoms bonded to silicon permolecule and a viscosity at 25° C. of from about 5 mPa·s to about 2000mPa·s; wherein the proportions in weight of the organopolysiloxane A,the silicon chain extender B1, and the silicon crosslinker B2 are suchthat the overall molar ratio of the hydrogen atoms bonded to the siliconto the overall alkenyl radicals bonded to the silicon is from about 0.4to about 1.5; and wherein, upon inclusion of between about 9% to about20% by weight of the hollow glass beads D to at least one of package P1and P2, the combination of P1 and P2 provides a composition having aviscosity at 25° C. from 500 mPa·s to 5,000 mPa·s and is capable offilling a battery module casing.
 22. The kit of claim 21, upon inclusionof between about 9% to about 20% by weight of the hollow glass beads Dto at least one of package P1 and P2, the combination of P1 and P2provides a composition having a viscosity at 25° C. from 500 mPa·s and2,500 mPa·s.
 23. The kit of claim 21, wherein the prepared siliconerubber syntactic foam is flame resistant.
 24. The combination of claim22, wherein the prepared silicone rubber syntactic foam is flameresistant.
 25. The kit of claim 21, wherein the silicon compound B (ii)has a weight ratio of the silicon chain extender B1 to the siliconcrosslinker B2 from about 6.2:1 to about 11.2:1.
 26. The kit of claim21, wherein the silicon compound B (ii) has a weight ratio of thesilicon chain extender B1 to the silicon crosslinker B2 from about 6.2:1to about 10.8:1.
 27. The kit of claim 21, wherein the silicon compound B(ii) has a weight ratio of the silicon chain extender B1 to the siliconcrosslinker B2 from about 6.2:1 to about 8.9:1.
 28. The kit of claim 21,wherein the at least two alkenyl groups bonded to silicon per moleculeof the organopolysiloxane A is selected from the group consisting ofvinyl, allyl, hexenyl, decenyl, tetradecenyl, and combination thereof.29. The kit of claim 21, wherein the hydrosilylation catalyst C isselected from the group consisting of Karstedt's catalyst,platinum-based catalysts, rhodium-based catalysts, ruthenium-basedcatalysts, paladium-based catalysts, nickel-based catalysts, andcombinations thereof.
 30. The kit of claim 21, wherein the cure ratecontroller G is selected from the group consisting of vinyl-containingcyclic siloxanes, acetylenic alcohols, heterocyclic amines, alkylmaleates, olefinic siloxanes, polydiorganosiloxanes containing vinylradicals, and combinations thereof.